Select one of the 2 custom programs and press enter. Then the time will be flashing and this is where you select how long you want to the routine to last and then press enter. As before the calorie window will be flashing and here you enter your bodyweight. The pulse will flash and here you input your age and press enter.
Then we come to setting the speed and incline of the workout. This is the meat and guts of the routine you'll be doing and how hard or easy you make it for yourself. A segment will be flashing, here you set the speed using the fast and slow keys and then press enter, you'll be doing this for each segment of the workout. When finished the first segment will flash again for you to enter your incline levels.
When all this is done and you've entered your workout how you want it then press start. This will begin the workout and, more importantly, save it to memory. Now when ever you select that custom program your routine will appear until you change it and that's how you program the custom workout on a treadmill.
All treadmills that have custom programs will all enable you to modify them in a similar way. Remember to keep the user manual to refer to in case you run into any problems. If it comes to it I'm sure the customer service people would be able to help you if the worst should happen. After all, you pay a lot of money for a treadmill.
Like I said these are great for races where you can copy the layout of hills and maybe the speed you want to run at. They also useful as your fitness level progresses, running the same routine may become easier after a while. This is a good thing and happens as you get fitter. Then is the time to extend it or modify it further so it still challenges you.